


Sin Eater

by monicawoe



Category: Supernatural
Genre: Blood Drinking, Boy King of Hell Sam Winchester, Demon Dean Winchester, Gen, Mark of Cain (Supernatural), Sam Winchester Drinks Demon Blood From Dean Winchester, Sam Winchester's Demonic Powers, Season/Series 10
Language: English
Status: Completed
Published: 2020-07-11
Updated: 2020-07-11
Packaged: 2021-03-05 04:42:10
Rating: Mature
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 1,239
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25208665
Author URL: https://archiveofourown.org/users/monicawoe/pseuds/monicawoe
Summary: Sam has a different plan to cure demon Dean, but Dean doesn't want to be cured.(written as a bday gift for Quickreaver; inspired bythis amazing art)
Relationships: Dean Winchester/Sam Winchester
Comments: 21
Kudos: 189





	Sin Eater

**Author's Note:**

  * For [quickreaver](https://archiveofourown.org/users/quickreaver/gifts).
  * Inspired by [Bitumen Kiss](https://archiveofourown.org/works/25286686) by [abitingsmile](https://archiveofourown.org/users/abitingsmile/pseuds/abitingsmile). 



> thanks to wetsammywinchester for the lightning fast beta

"There's more than one way to cure you," Sam said, and he sounded tired.

Good. Dean was getting tired too—of explaining himself. "Told you, Sammy, I don't want to be cured."

"I know," Sam said. "But then...you never cared about what I wanted, did you?"

"Excuse me?" Dean glared up at him from the chair he'd been bound to. "I saved your life."

"I didn't want to be saved either," Sam said, with a sigh that sounded less like resignation and more like bitter acceptance. "See, we've been going about this all wrong."

"We have?" Dean asked, straining against his bonds one more time. Then he fell still because Sam was stripping off his t-shirt, tossing it aside carelessly onto the floor.

"We have," Sam repeated, stepping closer as he pulled a knife from his belt sheath and looked down at Dean.

And Dean _knew_ that look, he'd seen it on Sam before paired with a bloodied smile and for this first time since he'd been reborn with this black veil covering his thoughts he felt a tinge of fear. "You can't cure me with that."

Sam ignored him and grabbed Dean by the hair, pulling his head back, baring his throat.

Dean fought him, or tried, but it was an awkward, humiliating angle and between the devil's trap and the etchings in the chair Sam had trapped him in, his demonic strength was pretty much unusable. The tip of the blade pressed against the tender skin beneath Dean's Adam's apple for one long moment, and all Dean could hear was his heartbeat or maybe it was Sam's, before Sam pulled the blade across, slicing Dean's throat open.

The blade had cut deep, and Dean felt a twin sting of cold air and burning heat as his blood welled out.

Sam released his hold on Dean's hair, just enough for Dean to get a glance of his brother lunging down at him before he clamped onto his throat, chasing any lingering coolness away. There was a beat of absolute quiet as Sam lathed his tongue over Dean's wound, and Dean recoiled and reveled at the intimacy of it, but the noises Sam was making quickly overrode everything else. Dean had never heard him make sounds like that: deep, guttural, and hungry. He thought he'd probably made noises like that himself once or twice, over a hamburger or with a particularly good orgasm, but feeling the vibration of Sam's growls against his throat was something entirely different. Dean pulled against his bonds again but for entirely different reasons this time. Even if he could get away, he wasn't sure he would. The mark on his arm throbbed angrily, the blood spilled wasn't supposed to be his own, but its pull weakened the more Sam drank and Dean himself felt subdued, calmer, like a heavy blanket was covering him, making his limbs weigh a ton.

Breathless, Sam came up for air, pupils blown wide and solid black.

Dean grinned at him. "I taste good, huh?"

Sam started chanting, something Dean recognized vaguely from the tones—too fast to be Enochian, but an ancient tongue that Sam spoke with ease like it was something he'd practiced. Something he'd planned. The walls around them started to tremble, the harsh lights of the dungeon sputtering and then shattering, one by one. The room filled with a wholly different light, something red and gold, as familiar as a scalpel in his hand and a soul on a rack.

"What are you doing?" Dean asked as Sam pressed on, ignoring him as he continued the invocation, eyes closed.

That heavy pull on Dean's limbs intensified, the weight around his ankles becoming painfully strong, and he craned his neck until he could see the floor enough to note that it was coated in a void-black ooze, shiny and undulating. It looked _alive_. "Sam," Dean said, suddenly acutely aware that whatever was happening was completely beyond him. Whatever Sam was doing was going to consume them both. "Sam, stop!"

But Sam didn't stop, and the dark mass pooled up around them, rising like a swelling tide until the room was filled wall to wall. It kept climbing, countless gallons a second until it lifted them off the floor.

The pulling darkness reached Dean's bound wrists and seeped up, thin tendrils of it reaching for the mark, tracing its contours like a caress. And then as Sam's words grew louder, the pain set in, a searing heat as the mark throbbed and pulsed with hellfire. Dean remembered the feel of that particular flame, had suffered through it himself for decades before discovering the joy of using it on others—a slow, liquid-nitrogen-thawing burn that went deeper than bone. The magic-heavy tint in the air grew a deeper red as Sam belted out the next few words but Dean couldn't make sense of them, drowning in the pain spreading from the searing mark out into his veins. His heart was beating heavier, a strange rhythm more like a bass drum, every word from Sam pulling out another resounding thump, thump, thump. The hellfire climbed up higher, nestling in his chest and he could see it now, veins glowing brightly beneath his skin.

Sam finished the invocation with one final _"pātakah,"_ and opened his eyes again. They glowed a bright, gilded yellow. He smiled at Dean with bloodied teeth and swiped his long fingers over the still weeping wound on Dean's neck. His eyes never left Dean's as he brought his red-coated fingers to his mouth and sucked them clean. The pain in Dean receded, and then stopped all at once.

“Hell of a cure, Sammy,” Dean said, breathless.

“Wait,” Sam said, reaching languidly down into the black, twining his fingers around Dean’s. The rope around Dean's wrists crumbled away and Sam raised their joined hands, moving with ease through the sludge. Both their arms came out clean, Dean's forearm unmarred by the mark, his flesh completely bare. Healed.

"What did you do?" he asked, voice trembling.

"I cured you," Sam said and took a deep breath, his eyes shining more brightly for a moment before settling into a darker shade of royal amber. He thrust his hands back down into the oily black and all around them the oozing sea receded, rapidly, like someone had pulled the drain.

But Dean tore his eyes away from the impossible scene around him when he realized where it was all going. The veins in Sam's arms were darkening, charring from the inside, going from pale blue to midnight black, more of them with every passing second until his brother's torso was covered in a dark spiderweb of swollen veins. Sam's breathing quickened but he didn't look like he was in pain, if anything, he looked content, woozy, and heavy-lidded like he was drunk. The last of the oil-slick clung to Sam's fingers in thick tendrils that retracted, suctioned up into him like all the rest, and when it was all gone, the floor bone-dry once again, Sam collapsed to his knees, eyes falling shut.

Dean stood, on shaky legs. He felt different. Weak. Human.

Sam steadied himself, one hand on the dungeon floor, then pushed himself up to standing, meeting Dean's gaze with his golden eyes.

"What did you do?" Dean asked again.

But Sam didn't answer, he just smiled one last time, lips and chin stained red, and then vanished.


End file.
